how much rotor rub if any is normal?

[Bushranger]

Tell me how much rotor rub do you think is normal and acceptable if any.

I'm currently at the point where there is a just a light twing twice on every revolution. I played around with truing the rotor itself and it fixed almost all the problem, but still just two little spots.

People I speak to say don't worry about it and think I'm being a bit OCD about it. It certainly doesn't noticably slow the wheel down significantly when spinning freely.

I think manufacturers really need to come up with a better method where the gap is slightly larger.

It drives me nuts.

 

[outtacontrol]

Yep, me too.

I have low spec Shimano's that regularly get some rub, especially after a long downhill with lots of braking, or after re installing wheels.

I have given up trying to work out why it happens, I just loosen the calliper and re align again.

As an interesting aside, I asked about it at the LBS once and was told that it was very common for rotors to slightly out of true, from new. They showed me quite a few brand new bikes that had some slight rub on the showroom floor.

 

[Registered Nutcase]

Best thing you can do is get a floating rotor.gets rid of that and they dont warp from the heating/cooling.

Unfortunatly I dont know if they are made in 6/7"

 

[harmonix1234]

I don't think any rotor rub is acceptable, and I am constantly fiddling to get mine clear.
Every time I rebuild my hub, or take the rotor off for whatever reason it always 'chings' a few times on each rotation when I put it back together.
I am like you, but I actually do have OCD so here's a few things that I have noticed.

Sometimes, it can be a matter of a fraction of a millimeter, and it may be rectified by the minute difference that's made when you either tighten or loosen your QR skewer by a quarter of a turn. Or less.

Another thing I have done is place a small piece of foil folded two or three times in between the dropout and axle and sandwich it in there before you tighten your QR skewer. Push down hard on the wheel first to make sure it settles. It only needs to be very thin, don't go putting wads of the stuff in there. Try each dropout and see which one works. I know this sounds really ghetto but the difference of only a fraction of a degree in the rotors angle can make a difference... When you have OCD.

Also, you can take out the brake pad(s) and get some very fine sand paper and take a small amount off. You will find that rotor rub is usually on the high or the low side of the pad so just round the edges of the top and bottoms first before you go wittling the bulk off and see if it helps. They disappear pretty quick on the grit so use something fine like 400 grit. And take it easy.

One more thing, you know the little X style spring steel clips that hold the pads in against the pistons? Get some needle nosed pliers and ever so slightly bend them outwards so that when the brake lever is not engaged there is absoluteley no chance of any space being between the pad and piston.

When straightening the rotor, Find a quiet spot, turn off the tele/radio so you can really hear every little 'ching'.
I find that putting your bike on a workstand / milk crate / whatever you can find and I get a torch and place it in a sneaker pointing up (if it's too bright put some paper over the torch), and shine it up through the brake housing as I spin the wheel.
This helps as it silhouettes the rotor and brake assembly against the light background and makes it really easy to see when and where the rotor is rubbing as it comes into contact with the pad. Or you could just put a piece of white paper on the ground... But I have OCD, so it's the torch for me.

I have 180mm rotors on deore centrelock hubs.

It's just a matter of not rushing it and setting some time aside to just nail it.

Good luck!

 

[Mark S]

I have low spec Shimano's that regularly get some rub,

To create a plural, simply adding an "s" is sufficient.

 

[Stevob]

That's some nice OCD there harmonix1234...and Mark S.

FWIW, I have rotor rub OCD myself.

 

[evObda2]

I dont think the problem lies in the brake.. but more the rotor here.
But depending on how warped your rotor is (sounds only slightly) different brand brakes have adjustment to try and help in this.
I find different brake pads heat up more than others too so this may have an effect on the rotor?

Someone said floating rotors, which work well, and help to give a consistent straight rotor and brake feel (I use Hope 180mm on my dh bike). However a decent set of new standard rotors should be sufficient to get rid of the problem i would think.

Also how are you installing your calliper? By doing the old loosen the bolts, hold the lever then re-tighten?

Worst case, id just buy some nice new rotors (think i may even have some new 160mm ones here lying around i could sell) and some new pads, brake bleed and see how that goes.

 

[niftydog]

A small amount of rotor rub is inevitable. It is also often temporary, and will come and go from one minute to the next.

It is often a matter of a fraction of a millimetre - so lets think about what might cause a fraction of a millimetre discrepancy:

• thermal effects on the rotor
• thermal effects on the brake fluid
• slight changes in the piston return position
• slight change in the position of the pad on the piston
• a bit of dirt on the pads
• slight misalignment when installing wheels
• a change in air pressure or temperature
• a butterfly might even have sneezed on your rotor!

etc etc etc.

Try this - set up the light as described in harmonix1234's post, then get a finger on one of the tabs protruding from one of the pads and give it a wiggle. See how much the pad can move around in there!? Still think a fraction of a millimetre is worth worrying about?

Chances are any tiny noise will change or disappear completely after the first moderately hard pull on the brakes. Chasing tiny noises that you have to put your ear up to the brake in order to hear is OTT.

Test by lifting the wheel and spinning - if the wheel stops spinning long before you think it should then there's a somewhat significant amount of friction and you might want to tend to it.

 

[outtacontrol]

To create a plural, simply adding an "s" is sufficient.

Thanks for your contribution.

Save it for your students.

 

[frensham]

Thanks for your contribution.

Save it for your students.

Nah, oim wif Mark S on this wonn. Learn to youse apostraphe's correctly.

 

[Craftworks]

First, just try flicking the lever in a couple of times to reset the pistons..

The clearance between the pads and rotor is achieved by the elastic properties of the piston seal. When you apply the brakes the piston only slides through the piston seal after the seal cannot deflect any more, when you get off the brakes the seal deflects back into its resting position dragging the piston back into position - this allows the brakes to be self-adjusting while provide a resetting action.

If you don’t have your calliper centred and aligned properly in the first place, your brake pads will wear unevenly causing the resetting to be less effective.

 

[digitalhippie]

First, just try flicking the lever in a couple of times to reset the pistons...

That does the trick for me too. Occasionally the front brake develops a light ping, no real pattern to when it happens that I can tell. A few sharp goes on the brake, voila!

Since the weather has turned wet again though good chance to fiddle around with stuff, reset the brakes etc.

 

[JX8P]

these tips are good!
i have this issue from time to time, thanks!

 

[outtacontrol]

First, just try flicking the lever in a couple of times to reset the pistons..

The clearance between the pads and rotor is achieved by the elastic properties of the piston seal. When you apply the brakes the piston only slides through the piston seal after the seal cannot deflect any more, when you get off the brakes the seal deflects back into its resting position dragging the piston back into position - this allows the brakes to be self-adjusting while provide a resetting action.

If you don’t have your calliper centred and aligned properly in the first place, your brake pads will wear unevenly causing the resetting to be less effective.

You sound like have more idea than my LBS when I raised this issue with them.

I have Shimano M475 hydros that I have an issue with the back, where the lever has to travel through it's action until it is almost on the bars before it works. It is not anything to do with blade adjustment, as it is the same regardless where the lever starts it's stroke.
It feels like the pads are sitting too far from the rotor and has to travel a long way before contacting the rotor. It appears that they are not self adjusting?
It only happens with the back.

I find if I pull the wheel out and pull my brakes on to push the pistons out, I can fix the problem. Sometimes it goes too far and I have to lever them back in a bit, but with a bit of fiddling, I can get the brake contacting at the start of the lever stroke.

How does your explanation relate to this issue??

 

[harmonix1234]

You sound like have more idea than my LBS when I raised this issue with them.

I have Shimano M475 hydros that I have an issue with the back, where the lever has to travel through it's action until it is almost on the bars before it works. It is not anything to do with blade adjustment, as it is the same regardless where the lever starts it's stroke.
It feels like the pads are sitting too far from the rotor and has to travel a long way before contacting the rotor. It appears that they are not self adjusting?
It only happens with the back.

I find if I pull the wheel out and pull my brakes on to push the pistons out, I can fix the problem. Sometimes it goes too far and I have to lever them back in a bit, but with a bit of fiddling, I can get the brake contacting at the start of the lever stroke.

How does your explanation relate to this issue??

It sounds like you need a little more fluid in the line / have some air in the line.
Just a guess.

 

[outtacontrol]

It sounds like you need a little more fluid in the line / have some air in the line.
Just a guess.

Check.

Been bled twice, once by LBS and once by myself (because I was unhappy with the result from LBS).

As I said, the only success I have had is to remove the wheel and deliberately close the pistons by pulling on the brake.

I have heard horror stories about people doing this, but I have to try really hard to get them to move together. Maybe this could be a clue??

 

[donny70]

To create a plural, simply adding an "s" is sufficient.

I've added an "s" and now my rotor rubs more than ever. Oh no!

But seriously, great tips. I'm sick of hearing that ching ching noise as I ride. Off to the garage with me...

 

[rstwosix]

I'm the brake setup expert at our shop. I won't stop until I've gotten rid of rotor rub. The problem is usually caused by:
1. Bent rotor
2. Pads too close to rotor (usually Avid problem)
I've spent years at this, so I can usually straighten a bent rotor (with my Park Tools brand rotor tool) in a few minutes. It takes practice,patience and complete quiet. If a rotor is too bent I replace it.
If the pads are too close to the rotor I follow the usual procedure of pressing the pistons back into the caliper. Sometimes this is unachievable without letting out a slight amount of brake fluid.

 

[ramr1]

I'm the brake setup expert at our shop. I won't stop until I've gotten rid of rotor rub. The problem is usually caused by:
1. Bent rotor
2. Pads too close to rotor (usually Avid problem)
I've spent years at this, so I can usually straighten a bent rotor (with my Park Tools brand rotor tool) in a few minutes. It takes practice,patience and complete quiet. If a rotor is too bent I replace it.
If the pads are too close to the rotor I follow the usual procedure of pressing the pistons back into the caliper. Sometimes this is unachievable without letting out a slight amount of brake fluid.

I needed some new pads for my rear (Hayes). Labour was cheap so I got the LBC to replace them for me. After they were installed there was a bit of rub. The guy there said it was normal for this to happen when installing new pads. I thought he was full of sh!t. I have isntalled so many pads on several cars and never have this happen. Never worked on bikes but thought it should be rub free.

After going for a ride the rubbing got worse. The wheel would spin 2 revolutions untill it seized. I got rid of most of it by losening the mounting bolts and retightening. Went for another ride and now it's back. The rotor looks to be straight enough.

I guess the rub doesn't really affect speed but it's just really annoying.

 

[DuncanFG]

Another thing to look at is a dirty/sticky piston. This is often a problem on shimano hydros.
Usually this can be fixed by wiping some brake cleaner / metho on the piston with one of those ear cleaner things or looping a strand of rag around them.

It works better the more piston you can expose but be careful not to pop it out as that will require a full rebleed. If the piston is really stuck you may have to hold the other one back while you squeeze.

Just in the last week I've had two particularly stubborn pistons that cleaning wouldn't fix. Applying a drop or two of mineral oil (or I suspect brake fluid on DOT brakes) to the piston then pushing them back in made them work perfectly again. I suspect the problem was a dry seal.

NB: Do not get any oil on the pads or rotor as this will dramatically reduce their power. Remove the pads and the wheel first to be sure and wipe up any excess.